Macrofilamentary yarns

ABSTRACT

Cord suitable for conveyor belts and tire breaker belts comprises a plurality of individually twisted synthetic macrofilaments twisted together, each macrofilament having a denier of at least 100.

United States Patent Kenyon et al.

MACROFILAMENTARY YARNS Inventors: Derek Kenyon; Donald James Wilson, both of Harrogate, England Assignee: Imperial Chemical Industries Limited, London, England Filed: Oct. 6, 1969 Appl. N0.: 863,872

Foreign Application Priority Data Oct. 11, 1968 United Kingdom 48328/68 Got. 14, 1968 United Kingdom 48620/68 Nov. 5, 1968 United Kingdom 52417/68 US. Cl. 57/140 R; 152/359 Int. Cl D02g 3/48 Field of Search 152/359; 57/153, 140, 139;

References Cited UNITED STATES PATENTS 4/1944 Jackson et al. 57/153 X June 17, 1975 Primary Examiner-Donald E. Watkins Attorney, Agent, or Firm-Herbert M. Adrian, .lr.

[ 5 7] ABSTRACT Cord suitable for conveyor belts and tire breaker belts comprises a plurality of individually twisted synthetic macrofilaments twisted together, each macrofilament having a denier of at least 100.

8 Claims, 4 Drawing Figures PATENTEDJUN 17 ms 3 889 L457 Fig! Planar Distortion Fig. 2.

Total Planar Rigidity SQOO |Q ooo Rigidity per Unit Weight i Fig. 3

Distorting Force Fig.4

Ply separatism MACROFILAMENTARY YARNS The present invention relates to filamentary yarns or cords composed of macrofilaments and to rubber structures reinforced therewith, particularly, though not exclusively, radial-ply pneumatic tyres. By macrofilament" used herein is meant a monofilament having a denier greater than 50.

Textile filamentary cords have previously been described for use in the manufacture of conveyor belts and pneumatic tyres in order to reinforce such structures. A typical example ofa cord for reinforcing pneumatic tyres is one formed from synthetic filaments by twisting a plurality of such filaments to form a yarn and then twisting together a number of these filamentary yarns. The filaments usually have a denier of the order of 5 although filament deniers up to about 20 have been proposed.

According to the present invention, a synthetic filamentary cord comprises a plurality of individually twisted synthetic macrofilaments twisted together, each macrofilament having a denier of at least 100.

The invention also includes rubber structures reinforced with such cords.

The twist properties of the cord may be such that the twist levels in the singles macrofilaments and in the cord are opposite and balanced. For this condition the relationship between the twist levels is given by Singles twist Cord twist x V N where N is the number of macro filaments.

The cord may also have a twist level which is equal and opposite to the twist level of the singles macrofilaments. Any twist liveliness in the cord may be reduced or eliminated by subjecting the cord to a heat setting treatment.

The twist level in the cord should be between 2 and 12 turns per inch and is preferably 4 to 8 turns'per inch.

The denier of each macrofilament is in the range I to 1500, preferably 400 to 600, and the total denier of the cord is in the range 1000 to 10,000, preferably 2000 to 5000. It is preferable for the individual macrofilaments in the cord to be of the same denier.

Although, for a given cord denier, the number of macrofilaments forming the cord'is variable, it is preferred that the number of macrofilanients should be at least three and not more than twenty. A particularly desirable cord is one which is composed of seven macrofilaments.

Therefore, according to a preferred embodiment of the invention, a synthetic filamentary cord comprises seven, individually twisted, synthetic macrofilaments twisted together, each macrofilament having the same denier in the range 400 to 600. This preferred yarn is circular in cross-section due to the excellent packing characteristics of its seven macrofilaments which are arranged such that a sheath of six macrofilaments encompasses a core of one macrofilament.

The macrofilaments forming the cords of the present invention may be obtained by melt-extruding synthetic polymers, for example, polyesters, copolyesters, polyamides, and copolyamides. Particularly suitable and preferred synthetic polymers are poly(ethylene terephthalate) and poly (hexamethylene adipamide). It is preferable that each macrofilament should have a tenacity greater than grammes per denier.

Rubber structures reinforced with cords of the present invention exhibit a high degree of planar rigidity which makes them suitable for use in the construction of conveyor belts and particularly in the breaker structures of pneumatic tyres of the radial-ply type.

Accordingly, the present invention also provides a radial-ply pneumatic tyre comprising a carcass consisting of radial plies of textile material and a tread layer, a breaker structure disposed between the carcass and the tread layer, the breaker structure being formed of at least two plies or layers of parallel macrofilament cords embedded in rubber, each cord consisting of a plurality of individually twisted macrofilaments twisted together, each macrofilament having a denier of at least 100.

In each breaker ply, the macrofilament cords may be disposed at zero inclination or a small angle only, not exceeding 20", t0 the midcircumferential plane of the tyre; and the cords in one breaker ply may be disposed at zero inclination or a small angle only, not exceeding 40, to those in the adjacent breaker ply or plies.

That property of the reinforced structures of the invention, referred to herein as planar rigidity, is a particular importance in the region of the breaker plies of a radial-ply tyre. It is determined by the compression and the tensile moduli of the cords embedded in the rubber, although it depends to a greater extent on the smaller of these two modulus values which, in general, is the compression modulus. Considering the breaker plies as being a planar laminate structure, see FIG. 1 of the ac companying drawings, then the planar ridigity of the structure is defined as the resistance to shear and bending of the structure in the plane parallel with the reinforcing plies. When the breaker structure is forming part of a tyre then this place corresponds to the plane of the road contact patch of the tyre. The compression modulus of the breaker structure is essentially determined by the compression moduli of the macrofilament cords. The compression moduli of the cords of the present invention are greater than for multifilament cords of the prior art, resulting in breaker structures of increased planar rigidity per unit weight of reinforcement material. The compression modulus of the breaker structure of the tyre according to the invention should be at least 35,000 pounds per square inch.

The macrofilament cords have to be embedded in and firmly adhered to the rubber of the breaker region of the tyre. In order to achieve thelatter requirement it is desirable to use an adhesive which is specially prepared for the purpose of improving adhesion between cords formed of synthetic polymeric materials and rubber. For example, the adhesive Pexul (R.T.M.) is used to adhere polyester materials to rubber.

In order to achieve the maximum .planar rigidity of the breaker structure it has been determined that the macrofilament cord denier should be in the range 2,000 to 10,000, preferably 3000 to 5000. The basis for this range can be clearly seen from FIG. 2 of the accompanying drawings which illustrates the relationship between total planar rigidity and cord denier; further more the planar rigidity is increased the closer the breaker plies are positioned with respect to one another, as seen in FIG. 3 of the accompanying drawings which illustrates the relationship between breaker ply separation and planar rigidity per unit weight.

If desired, the planar rigidity of a reinforced rubber structure according to the invention can be markedly increased by dispersing staple fibres in the rubber interlayer(s) between the two (or more) plies of macrofilament cords. Suitable staple fibres are from 0.125 to 3 inches long and have deniers in the range 1 to 5. The proportion of staple fibres present in a rubber interlayer is preferably between 5 to 25 percent based on the weight of elastomer. The staple fibres are preferably made from polyethylene terephthalate, although polyamide and rayon fibres are suitable.

The invention will be further described by reference to the following Examples.

EXAMPLE I A sample of a breaker structure for a type according to the invention and which consisted of twoplies of parallel 1 macrofilament cords of polyethylene terephthalate embedded in rubber was made as follows: Cord Production Three packages of single and macrofilaments, each macrofilament having a denier of 1000, were downtwisted on a conventional ring and traveller machine. These twisted single macrofilaments were then twisted to form a three-fold cord. Each macrofilament had 5 turns per inch S-twist and the cord had 5 turns per inch Z-twist.

Cord Preparation The cord was heat set and adhesive dipped by a single end treatment on a Litzler Computreater machine. The adhesive dip solution used was composed of one part of a percent Pexul (R.T.M.) solution to one part of a Resorcinol Formaldehyde Latex. The composition of the Latex was Water 650 parts Resorcinol 25 parts Formalin 14 parts Gen Tac" Latex 310 parts The heat setting and dip curing conditions were 240C for 30 seconds at 1 percent stretch applied to the cord. Construction of Sample Breaker Structure A cord ply was prepared by wrapping cord at ends per inch onto a rectangular plate, pressing a thin uncured rubber sheet onto the cords, cutting the cords embedded in the rubber sheet from the plate, and pressing a second rubber sheet onto the other side of the cords. A second cord ply was prepared in a similar manner.

The sample breaker structure was built up using sheets of uncurred rubber and the breaker plies as made above to form a structure having a length of 15 cm., a width of 5 cm., and a thickness of 0.7 cm. The cord plies were inclined at an angle of 20 to the longitudinal centre line of the sample and at an angle of 40 to each other. The separation between the cord plies was 1.0 mm. The sample breaker structure was then cured by heating at 150C for 30 minutes while being restrained in a mould.

The planar rigidity of the structure was measured and the result is given in Table I.

EXAMPLE II A comparative sample of a conventional breaker structure which consisted of two plies of multifilament cords of polyethylene terephthalate embedded in rubber was made according to the method described in Example Each cord was composed of three yarns which were plied together such that each singles yarn had 7 turns per inch S-twist and the resultant cord had 7 turns per inch Z-twist. Each yarn was made up of 192 filaments and had a denier of 1000. The planar rigidity of this structure is given in Table 1.

EXAMPLE III Table 1 Example No. Planar Rigidity/Unit Weight* *The weight is that of all the textile materials used in the reinforcement i.e. cord or cord and staple fibres.

The .values of planar rigidity for the tested samples were based on the resultsderived fromsubjecting each sample to a simple test performed by an Instron tensile tester (Instron is a Registered Trade Mark). The Instron tester is adapted to induce a planar distortion to a sample, as illustrated in FIG. 4 of the accompanying drawings. A graph can'be obtained of the distorting force against the amount of distortion as measured by the upward deflection of the centre of the sample. For comparing the performance of different reinforcements, the following arbitrary definitions are applied:

i. Block Planar Rigidity:- Excess distorting force required to distort the block 1.5 mm. to 2.5mm. at an lnstron speed ofv 5 mm./minute.

ii. Reinforcement Density: The number of cords ends per centimetre per ply multiplied by cord denier (plus the weight/volume of staple fibre when present).

iii. Planar Rigidity per Unit Weight:- Planar Block Rigidity (reinforced sample) minus Planar Block Rigidity (plain rubber sample) divided by the Reinforcement Density.

What we claim is:

l. A synthetic filamentary cord comprising a plurality of individually twisted synthetic macrofilaments which are also twisted together, each macrofilament being a monofilament having a denier in the range of 400 to 600, and wherein the twist level in the cord is between 2 and 12 turns per inch and the denier of the cord is in the range of 1,000 to 10,000.

2. A cord according to claim 1, wherein the cord twist level is 4 to 8 turns per inch.

3. A cord according to claim 1, wherein the cord denier is in the range 2000 to 5000.

4. A cord according to claim 1, wherein the number of macrofilaments is at least three and not more than twenty.

5. A synthetic filamentary cord comprising seven, individually twisted, synthetic macrofilaments twisted together, each macrofilament having the same denier in the range 400 to 600.

6. A cord according to claim 1, wherein each macrofilament has a tenacity of at least 5 grammes per demer.

7. A cord according to claim 1, wherein each macrofilament is made from poly(ethylene terephthalate).

8. A cord according to claim 1, wherein each macrofilament is made from poly(hexamethylene adipamide). 

1. A SYNTHETIC FILAMENTARY CORD COMPRISING A PLURALITY OF INDIVIDUALLY TWISTED SYNTHETIC MACROFILAMENTS WHICH ARE ALSO TWISTED TOGETHER, EACH MACROFILAMENT BEING A MONOFILAMENT HAVING A DENIER IN THE RANGE OF 400 TO 600 , AND WHEREIN THE TWIST LEVEL IN THE CORD IS BETWEEN 2 AND 12 TURNS PER INCH AND THE DENIER OF THE CORD IS IN THE RANGE OF 1,000 TO 10,000.
 2. A cord according to claim 1, wherein the cord twist level is 4 to 8 turns per inch.
 3. A cord according to claim 1, wherein the cord denier is in the range 2000 to
 5000. 4. A cord according to claim 1, wherein the number of macrofilaments is at least three and not more than twenty.
 5. A synthetic filamentary cord comprising seven, individually twisted, synthetic macrofilaments twisted together, each macrofilament having the same denier in the range 400 to
 600. 6. A cord according to claim 1, wherein each macrofilament has a tenacity of at least 5 grammes per denier.
 7. A cord according to claim 1, wherein each macrofilament is made from poly(ethylene terephthalate).
 8. A cord according to claim 1, wherein each macrofilament is made from poly(hexamethylene adipamide). 